1. Field of the Invention
The present invention relates to an electrodeless lamp system, and particularly, to a bulb used in an electrodeless lamp system.
2. Description of the Background Art
An electrodeless lamp system is a device for lighting by forming an electric field using microwave in a bulb unit in which a luminous material which illuminates by forming plasma due to the electric field.
Generally, when the electrodeless lamp is turned off, the electrodeless lamp system can be re-lighted after a certain time (tens of seconds˜a few minutes) has passed, since a mean free path of an electron having energy for forming plasma is not ensured due to high pressure of neutral gas, that is, the buffer gas filled together with the luminous material in the bulb unit.
In a case in which Xenon Xe is used as the buffer gas, light efficiency is improved about 5% more than in a case in which Argon Ar gas is used. However, a collision cross-section of Xe is large, and therefore, it is difficult to discharge in a high pressure state.
Therefore, in the conventional art, in order to reduce the re-lighting time of the electrodeless lamp system, a strong wind is blown directly to the bulb unit to cool down the bulb and to decrease the pressure in the bulb unit, however, problems such as increased cost due to additional devices, reliability of the additional devices, utilization of a space around the bulb unit, and light screening by the additional devices are generated.
Also, in a case of a light source of small size, that is, in a case of the bulb unit for a point light source (an arc gap is less than 2 mm), there should be an auxiliary device for initial light emitting.